A novel surface morphology for pipelines using transverse microgrooves was proposed in order to reduce the pressure loss of fluid transport. Numerical simulation and experimental research efforts were undertaken to evaluate the drag reduction performance of these bionic pipelines. It was found that the vortex ‘cushioning’ and ‘driving’ effects produced by the vortexes in the microgrooves were the main reason for obtaining a drag reduction effect. The shear stress of the microgrooved surface was reduced significantly owing to the decline of the velocity gradient. Altogether, bionic pipelines achieved drag reduction effects both in a pipeline and in a concentric annulus flow model. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were obtained by an orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% could be achieved. The numerical simulation and experimental results were cross-checked and found to be consistent with each other, allowing to verify that the utilization of bionic theory to reduce the pressure loss of fluid transport is feasible. These results can provide theoretical guidance to save energy in pipeline transportations.

Novel surface morphology of pipeline with transverse microgrooves was proposed for reducing the pressure loss of fluid transport. Numerical simulation and experimental research efforts were undertaken to evaluate the drag reduction performance of bionic pipeline. The computational fluid dynamic calculation, using SST κ-ω turbulent model, shown that the “vortex cushioning effect” and “driving effect” produced by the vortexes in the microgrooves were the main reason for the drag reduction. The shear stress of the microgrooved surface was reduced significantly owing to the decline of the velocity gradient; then bionic pipeline achieved drag reduction effect in the pipe and concentric annulus flow. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were obtained by orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% was achieved. The numerical simulation and experimental results were cross-checked and consistent with each other to verify that the utilization of bionic theory to reduce the pressure loss of fluid transport is feasible. Results can provide theoretical guidance for the energy saving of pipeline transportation.

Granular damping is a passive vibration control method that has attracted considerable attention in mechanical and structural vibration reduction. To reveal the energy dissipation mechanism of granular dampers under sinusoidal excitation, this study develops a numerical model of a granular damper based on the discrete element method (DEM). First, two damper construction methods—using particle elements and clump elements—are compared, and the clump element approach is selected to construct the damper. The friction coefficient and normal critical damping ratio are then calibrated using the Hertz contact model and single-particle bounce experiments. On this basis, a forced vibration system with a virtual spring is established, and numerical simulations are carried out under three sinusoidal excitation conditions: 0.4 cm-15 Hz, 1.0 cm-15 Hz, and 0.4 cm-45 Hz. The damping mechanism is analyzed from an energy perspective, with discussion of the impact force, displacement, and velocity responses. The results show that the damping particles accelerate the system’s approach to steady-state vibration. Energy dissipation occurs mainly during collisions between the damping particles and the inner wall of the damper, and collision dissipation is greater than friction dissipation. When the particles detach from the wall, the inter-particle forces are very small, and the energy dissipation is negligible. The particle–wall impact force exhibits a multi-peak profile, and the force–time ratio increases with excitation intensity. These findings deepen the understanding of granular damping mechanisms and provide a reference for the design and optimization of granular dampers.

Severe drill-string–wellbore friction during slide drilling limits axial-load transfer and reduces drilling efficiency in extended-reach horizontal wells. To investigate the mechanical response of a horizontal drill string under axial vibration, a three-dimensional geometrically nonlinear finite element model was developed in Abaqus/Explicit. The model incorporates a previously validated dynamic friction formulation and directly accounts for deformation-dependent drill-string–wellbore contact, allowing the coupled effects of axial vibration, friction, load transfer, and lateral deformation to be captured. Numerical results show that axial vibration markedly alters the spatial and temporal distributions of axial force and sliding velocity. Periodic modulation and reversal of axial velocity induce synchronous reversal of the friction force, which constitutes the dominant friction-reduction mechanism under the investigated conditions. The reduced effective friction improves axial-load transfer, increases WOB, and produces a more continuous drilling response, although larger WOB fluctuations are introduced. The vibration effect attenuates with propagation distance, indicating a spatially limited effective range of the axial oscillation tool. Under high axial compression, buckling increases drill-string–wellbore contact and deteriorates load-transfer efficiency. Axial vibration further reduces the externally applied compressive load required to reach sinusoidal and helical buckling, with a maximum reduction of approximately 12.9% in the investigated cases. These results provide a mechanical basis for balancing friction reduction, dynamic bottom-hole loading, load-transfer improvement, and drill-string stability in the application of axial oscillation tools, thereby helping to improve drilling energy efficiency and enhance the development capabilities of unconventional oil and gas resources.

The actuator is a key component of the creaming tool in drilling applications. Its jet performances determine the effective reaming efficiency. In this work, a new selective reaming tool is proposed and the RNG k-ε turbulence model is used to calculate its internal and external flow fields. In particular, special attention is paid to the design of the flushing nozzle. The results show that the jet originating from the flushing nozzle has a significant influence on rock cutting and blade cooling effects. In turn, the jet performances depend on geometric structure of the creaming actuator. In this framework, a conical-cylindrical nozzle with a diameter of 7 mm is initially considered as a basis to implement a strategy to optimize the structural parameters of the reaming actuator, and improve the related side tracking reconstruction technology.